Fluid purification methods and devices

Abstract

Disclosed is a method of purifying fluid, typically an aqueous fluid steam, with the method involving at least two reverse osmosis stages with retentate from a first reverse osmosis stage being subjected to the second reverse osmosis stage, and with intermediate treatment of retentate from the first reverse osmosis stage by exposure to an electric field. The intermediate treatment may involve electrocoagulation to remove sparingly-soluble compounds and permit enhanced reverse osmosis recovery. Additional treatment may be performed prior to the first reverse osmosis stage, between the first reverse osmosis stage and the intermediate treatment with an electric field, between such intermediate treatment and the second reverse osmosis stage, or after the second reverse osmosis stage.

What is claimed is: 
     
       1. A method of fluid purification comprising:
 a. processing a fluid stream by a first reverse osmosis stage to create a reverse osmosis retentate; 
 b. electrocoagulation treatment of at least a portion of the reverse osmosis retentate to an electric field to create a purified retentate; 
 c. after the electrocoagulation treatment, contacting the purified retentate with a polymer capable of promoting coagulation of sparingly-soluble compounds; 
 d. after the exposing, first injecting a first oxidizing agent selected from the group consisting of ozone, chlorine, potassium permanganate and combinations thereof, into the purified retentate; 
 e. after the contacting and first injecting, holding the purified retentate in a tank to allow settling of solid particles; 
 f. after the holding, first filtering the purified retentate with a first filtration treatment selected from the group consisting of ultrafiltration and microfiltration; 
 g. after the first filtering, second injecting a second oxidizing agent selected from the group consisting of ozone, chlorine, potassium permanganate and combinations thereof, into the purified retentate; 
 h. after the second injecting, third filtering the purified retentate with a multimedia filtration treatment selected from the group consisting of manganese dioxide filtration, KDF filtration, calcite filtration, magnesium hydroxide filtration, carbon filtration and combinations of these filtration treatments; 
 i. after the third filtering, fourth filtering the purified retentate with a second filtration treatment selected from the group consisting of cartridge filtration, ultrafiltration and microfiltration; and, 
 j. after the fourth filtering, processing at least a portion of the purified retentate by a second reverse osmosis stage to create a purified fluid. 
 
     
     
       2. The method of  claim 1 , wherein the fluid stream is an aqueous fluid stream. 
     
     
       3. The method of  claim 1 , wherein the fluid stream is pretreated by combining with an agent selected from the group consisting of a scale inhibitor, an acid, a reducing agent and combinations thereof, prior to the processing by the first reverse osmosis stage. 
     
     
       4. The method of  claim 1 , wherein the reverse osmosis retentate is combined with an agent selected from the group consisting of a polymer that will neutralize a scale-inhibiting polymer, an acid, a base, calcium hydroxide and combinations thereof, prior to the exposing to the electric field. 
     
     
       5. The method of  claim 1 , wherein at least a portion of the purified retentate is returned to combine with the fluid stream to be processed by the first reverse osmosis stage. 
     
     
       6. The method of  claim 1 , wherein the electrocoagulation treatment comprises adding dissolved metal ions of electrode material into the at least a portion of the retentate being treated during the electrocoagulation.